DEFINING PRESENT RATES OF SEA-LEVEL CHANGE AROUND NEWFOUNDLAND BY ANALYSIS OF TIDE-GAUGE RECORDS

A transect across Newfoundland and adjacent locations in Quebec and Nova Scotia affords the opportunity to investigate differential rates of sea-level change due to long-term glacioisostatic adjustment. Previous studies indicated differential rates of change in this area, but were somewhat limited by the duration of available records (Emery and Aubrey, 1991; Pirrazoli, 1991). The objectives of this work are to re-analyze these records including a decade or more of additional data, analyze data from sites not included in these earlier surveys, and analyze the data to better determine what additional factors (seasonality, interannual variability) influence these records. Rates of relative sea-level change from long-term (>22 yr) tide-gauge records vary from +2.3 mm/yr (Port-aux-Basques, NF) to -0.7 mm/yr (Harrington Harbour, QC). Local relative sea-level change at Port-aux-Basques was previously determined to be falling 1.8 mm/yr (Amery and Aubrey, 1991). Contours of vertical land movement based for the region were significantly influenced by this data point, and indicated the greatest rebound in the southwestern part of Newfoundland. Rates of sea-level change determined in this study indicate the greatest rebound along the Northern Peninsula and a simpler pattern of vertical land movement. In addition, preliminary wavelet analysis of data from three sites (Halifax, NS; Harrington Harbour, QC; St. John?s, NF) indicates that some variability in the records may not be accounted for by typical astronomic cycles or seasonal variables (e.g. the spring freshet). Further investigation will explore the possible influence of oceanographic variables on these records.